1. Field of the Invention
The present invention relates to a substrate processing apparatus and method for processing a substrate while transporting the substrate between modules, and to a non-transitory storage medium storing a program for implementing the substrate processing method.
2. Description of Related Art
In a semiconductor device manufacturing process, for example, predetermined processing of a semiconductor wafer (hereinafter simply referred to as “wafer”) is performed while wafers are sequentially transported by a substrate transport mechanism, called a transport arm, between a plurality of processing modules provided in a substrate processing apparatus, e.g. a coating/developing apparatus. When a wafer is transported, it is held by a holder provided in the transport arm.
There are cases where a wafer is held at a position displaced from a preset reference position in the holder due to a failure of a certain module or a failure of the transport arm itself. If such a failure becomes gradually larger, and therefore the displacement of the actual position of a wafer, held by the holder, from the reference position increases and an abnormality occurs in transport of the wafer, then a coating/developing apparatus indicates an alarm to the user and stops transport of wafers in the apparatus. However, because of displacement of the position of a wafer, held by the holder, from the reference position, the wafer will not be transferred to a proper position in a module. There is, therefore, the fear that wafers may continue to be processed in an abnormal manner in the module until the apparatus is stopped, resulting in poor processing of successive wafers.
Further, when wafer transport is stopped in a coating/developing apparatus due to a failure of a module, the stopping of transport will be continued until the module returns to normal operation. Even when wafer transport is stopped due to such a minor failure of a transport arm that can be easily corrected, the operation of the transport arm must be stopped. The stopping of wafer transport may therefore lower the operation rate of the coating/developing apparatus, resulting in decreased throughput.
Patent document 1 describes a technique involving correcting the amount of transport of a wafer between modules based on the position of a peripheral portion of the wafer, detected by a sensor, thereby eliminating a positional displacement of the wafer in the modules. Patent document 2 describes a technique involving determining the center position of a wafer from a detected position of a peripheral portion of the wafer and, based on a displacement of the center position from a predetermined reference position, controlling a transport arm so that it can transfer the wafer to a target transport position. These patent documents, however, fail to address the above-described problems, and the techniques disclosed cannot solve the problems.